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ec48314708
Design problems were discovered in the handling of composite types and record types that would cause some relevant versions not to be recorded. Misgivings were also expressed about the use of the pg_depend catalog for this purpose. We're out of time for this release so we'll revert and try again. Commits reverted:1bf946bd: Doc: Document known problem with Windows collation versions.cf002008: Remove no-longer-relevant test case.ef387bed: Fix bogus collation-version-recording logic.0fb0a050: Hide internal error for pg_collation_actual_version(<bad OID>).ff942057: Suppress "warning: variable 'collcollate' set but not used".d50e3b1f: Fix assertion in collation version lookup.f24b1569: Rethink extraction of collation dependencies.257836a7: Track collation versions for indexes.cd6f479e: Add pg_depend.refobjversion.7d1297df: Remove pg_collation.collversion. Discussion: https://postgr.es/m/CA%2BhUKGLhj5t1fcjqAu8iD9B3ixJtsTNqyCCD4V0aTO9kAKAjjA%40mail.gmail.com
324 lines
11 KiB
Plaintext
324 lines
11 KiB
Plaintext
<!--
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doc/src/sgml/ref/alter_index.sgml
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PostgreSQL documentation
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-->
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<refentry id="sql-alterindex">
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<indexterm zone="sql-alterindex">
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<primary>ALTER INDEX</primary>
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</indexterm>
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<refmeta>
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<refentrytitle>ALTER INDEX</refentrytitle>
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<manvolnum>7</manvolnum>
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<refmiscinfo>SQL - Language Statements</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>ALTER INDEX</refname>
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<refpurpose>change the definition of an index</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<synopsis>
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ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> RENAME TO <replaceable class="parameter">new_name</replaceable>
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ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> SET TABLESPACE <replaceable class="parameter">tablespace_name</replaceable>
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ALTER INDEX <replaceable class="parameter">name</replaceable> ATTACH PARTITION <replaceable class="parameter">index_name</replaceable>
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ALTER INDEX <replaceable class="parameter">name</replaceable> [ NO ] DEPENDS ON EXTENSION <replaceable class="parameter">extension_name</replaceable>
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ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> SET ( <replaceable class="parameter">storage_parameter</replaceable> [= <replaceable class="parameter">value</replaceable>] [, ... ] )
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ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> RESET ( <replaceable class="parameter">storage_parameter</replaceable> [, ... ] )
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ALTER INDEX [ IF EXISTS ] <replaceable class="parameter">name</replaceable> ALTER [ COLUMN ] <replaceable class="parameter">column_number</replaceable>
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SET STATISTICS <replaceable class="parameter">integer</replaceable>
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ALTER INDEX ALL IN TABLESPACE <replaceable class="parameter">name</replaceable> [ OWNED BY <replaceable class="parameter">role_name</replaceable> [, ... ] ]
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SET TABLESPACE <replaceable class="parameter">new_tablespace</replaceable> [ NOWAIT ]
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</synopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para>
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<command>ALTER INDEX</command> changes the definition of an existing index.
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There are several subforms described below. Note that the lock level required
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may differ for each subform. An <literal>ACCESS EXCLUSIVE</literal> lock is held
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unless explicitly noted. When multiple subcommands are listed, the lock
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held will be the strictest one required from any subcommand.
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<variablelist>
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<varlistentry>
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<term><literal>RENAME</literal></term>
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<listitem>
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<para>
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The <literal>RENAME</literal> form changes the name of the index.
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If the index is associated with a table constraint (either
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<literal>UNIQUE</literal>, <literal>PRIMARY KEY</literal>,
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or <literal>EXCLUDE</literal>), the constraint is renamed as well.
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There is no effect on the stored data.
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</para>
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<para>
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Renaming an index acquires a <literal>SHARE UPDATE EXCLUSIVE</literal>
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lock.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>SET TABLESPACE</literal></term>
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<listitem>
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<para>
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This form changes the index's tablespace to the specified tablespace and
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moves the data file(s) associated with the index to the new tablespace.
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To change the tablespace of an index, you must own the index and have
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<literal>CREATE</literal> privilege on the new tablespace.
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All indexes in the current database in a tablespace can be moved by using
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the <literal>ALL IN TABLESPACE</literal> form, which will lock all
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indexes to be moved and then move each one. This form also supports
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<literal>OWNED BY</literal>, which will only move indexes owned by the
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roles specified. If the <literal>NOWAIT</literal> option is specified
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then the command will fail if it is unable to acquire all of the locks
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required immediately. Note that system catalogs will not be moved by
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this command, use <command>ALTER DATABASE</command> or explicit
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<command>ALTER INDEX</command> invocations instead if desired.
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See also
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<link linkend="sql-createtablespace"><command>CREATE TABLESPACE</command></link>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>ATTACH PARTITION</literal></term>
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<listitem>
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<para>
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Causes the named index to become attached to the altered index.
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The named index must be on a partition of the table containing the
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index being altered, and have an equivalent definition. An attached
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index cannot be dropped by itself, and will automatically be dropped
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if its parent index is dropped.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>DEPENDS ON EXTENSION <replaceable class="parameter">extension_name</replaceable></literal></term>
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<term><literal>NO DEPENDS ON EXTENSION <replaceable class="parameter">extension_name</replaceable></literal></term>
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<listitem>
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<para>
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This form marks the index as dependent on the extension, or no longer
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dependent on that extension if <literal>NO</literal> is specified.
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An index that's marked as dependent on an extension is automatically
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dropped when the extension is dropped.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>SET ( <replaceable class="parameter">storage_parameter</replaceable> [= <replaceable class="parameter">value</replaceable>] [, ... ] )</literal></term>
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<listitem>
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<para>
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This form changes one or more index-method-specific storage parameters
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for the index. See
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<link linkend="sql-createindex"><command>CREATE INDEX</command></link>
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for details on the available parameters. Note that the index contents
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will not be modified immediately by this command; depending on the
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parameter you might need to rebuild the index with
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<link linkend="sql-reindex"><command>REINDEX</command></link>
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to get the desired effects.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>RESET ( <replaceable class="parameter">storage_parameter</replaceable> [, ... ] )</literal></term>
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<listitem>
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<para>
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This form resets one or more index-method-specific storage parameters to
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their defaults. As with <literal>SET</literal>, a <literal>REINDEX</literal>
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might be needed to update the index entirely.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><literal>ALTER [ COLUMN ] <replaceable class="parameter">column_number</replaceable> SET STATISTICS <replaceable class="parameter">integer</replaceable></literal></term>
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<listitem>
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<para>
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This form sets the per-column statistics-gathering target for
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subsequent <link linkend="sql-analyze"><command>ANALYZE</command></link> operations, though can
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be used only on index columns that are defined as an expression.
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Since expressions lack a unique name, we refer to them using the
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ordinal number of the index column.
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The target can be set in the range 0 to 10000; alternatively, set it
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to -1 to revert to using the system default statistics
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target (<xref linkend="guc-default-statistics-target"/>).
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For more information on the use of statistics by the
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<productname>PostgreSQL</productname> query planner, refer to
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<xref linkend="planner-stats"/>.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect1>
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<refsect1>
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<title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><literal>IF EXISTS</literal></term>
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<listitem>
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<para>
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Do not throw an error if the index does not exist. A notice is issued
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in this case.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="parameter">column_number</replaceable></term>
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<listitem>
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<para>
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The ordinal number refers to the ordinal (left-to-right) position
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of the index column.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="parameter">name</replaceable></term>
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<listitem>
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<para>
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The name (possibly schema-qualified) of an existing index to
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alter.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="parameter">new_name</replaceable></term>
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<listitem>
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<para>
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The new name for the index.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="parameter">tablespace_name</replaceable></term>
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<listitem>
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<para>
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The tablespace to which the index will be moved.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="parameter">extension_name</replaceable></term>
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<listitem>
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<para>
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The name of the extension that the index is to depend on.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="parameter">storage_parameter</replaceable></term>
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<listitem>
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<para>
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The name of an index-method-specific storage parameter.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><replaceable class="parameter">value</replaceable></term>
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<listitem>
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<para>
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The new value for an index-method-specific storage parameter.
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This might be a number or a word depending on the parameter.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>
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These operations are also possible using
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<link linkend="sql-altertable"><command>ALTER TABLE</command></link>.
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<command>ALTER INDEX</command> is in fact just an alias for the forms
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of <command>ALTER TABLE</command> that apply to indexes.
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</para>
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<para>
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There was formerly an <command>ALTER INDEX OWNER</command> variant, but
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this is now ignored (with a warning). An index cannot have an owner
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different from its table's owner. Changing the table's owner
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automatically changes the index as well.
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</para>
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<para>
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Changing any part of a system catalog index is not permitted.
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</para>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<para>
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To rename an existing index:
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<programlisting>
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ALTER INDEX distributors RENAME TO suppliers;
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</programlisting>
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</para>
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<para>
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To move an index to a different tablespace:
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<programlisting>
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ALTER INDEX distributors SET TABLESPACE fasttablespace;
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</programlisting>
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</para>
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<para>
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To change an index's fill factor (assuming that the index method
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supports it):
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<programlisting>
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ALTER INDEX distributors SET (fillfactor = 75);
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REINDEX INDEX distributors;
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</programlisting></para>
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<para>
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Set the statistics-gathering target for an expression index:
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<programlisting>
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CREATE INDEX coord_idx ON measured (x, y, (z + t));
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ALTER INDEX coord_idx ALTER COLUMN 3 SET STATISTICS 1000;
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</programlisting></para>
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</refsect1>
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<refsect1>
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<title>Compatibility</title>
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<para>
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<command>ALTER INDEX</command> is a <productname>PostgreSQL</productname>
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extension.
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</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<simplelist type="inline">
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<member><xref linkend="sql-createindex"/></member>
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<member><xref linkend="sql-reindex"/></member>
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</simplelist>
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</refsect1>
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</refentry>
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